No full official account of New Zealand’s participation in the First World War was ever published. Only four official volumes were published (1919-1923), and they were written by senior officers who had fought in the campaigns (Gallipoli, Sinai/Palestine, Western Front) but who generally had no training as historians. A useful summary on the genesis of the offical history can be found at Wikipedia.
Although providing detailed accounts of the fighting on the battlefields itself, they did not describe New Zealand during the war, its economy, politics or society, and the home-defence and patriotic efforts, New Zealanders in the naval or air war, and those serving with other British or Australian forces are not included. Despite this, the four official histories became accepted sources for New Zealand’s military effort in the Great War, and have never been updated or superseded.
The official history of the New Zealand Forces was written up in four volumes.
- Volume I: The New Zealanders at Gallipoli by Colonel Fred Waite, 1921
- Volume II: The New Zealand Division 1916 – 1919: A Popular History Based on Official Records by Colonel Hugh Stewart
- Volume III: The New Zealanders in Sinai and Palestine by Lieutenant Colonel Charles Guy Powler, 1922
- Volume IV: The War Effort of New Zealand by Lieutenant Henry Thomas Bertie Drew, 1923
Additionally, the following volumes can be found at the New Zealand Electronic Text Foundation as official histories, which I presume constitutes some kind of endorsement as “official” works.
- The Kia ora coo-ee : the magazine for the ANZACS in the Middle East, 1918
- ‘Something of Them Is Here Recorded’: Official History in New Zealandby Ian Callum McGibbon
- The Story of Two Campaigns: Official War History of the Auckland Mounted Rifles Regiment, 1914-1919 by Sergeant Charles Gordon Nicol
- Official War History of the Wellington Mounted Rifles Regiment 1914-1919 by Major Alexander Herbert Wilkie
- The History of the Canterbury Mounted Rifles 1914-1919 by Lieutenant Colonel Charles Guy Powles
- Official History of the Otago Regiment, N.Z.E.F. in the Great War 1914-1918 by Lieutenant Arthur Emmett Byrne
- The Auckland Regiment by Second Lieutenant Ormond Edward Burton
- The History of the Canterbury Regiment, N.Z.E.F. 1914 – 1919 by Captain David Ferguson
- The Wellington Regiment (NZEF) 1914 – 1919 by Major General William Henry Cunningham, Lieutenant Colonel Charles Archibald Lawrance Treadwell, Lieutenant James Sugden Hanna
- The Official History of the New Zealand Rifle Brigade by Lieutenant-Colonel William Semmens Austin
- Official History of the New Zealand Engineers During the Great War 1914-1919.
- With the Machine Gunners in France and Palestine by Major John Hector Luxford
- Regimental History of New Zealand Cyclist Corps in The Great War 1914-1918 by Officers of the New Zealand Cyclists Corp
- New Zealand Artillery in the Field, 1914-18 by Lieutenant John Richard Byrne
- The Maoris in the Great War by James Cowan
- The Samoa (N.Z.) Expeditionary Force 1914–1915 by Sergeant Stephen John Smith
- The New Zealand Medical Service in the Great War 1914-1918 by Andrew Dillon Carbery
- With the Trench Mortars in France by Lieutenant William Esmonde Lennox Napier
- With the Cameliers in Palestine by Sergeant John Robertson
- Ways and By-Ways of a Singing Kiwi with the N.Z. Divisional Entertainers in France by William Ernest McKinlay
- The Mounted Riflemen in Sinai and Palestine: The Story of New Zealand’s Crusaders by Lieutenant Arthur Briscoe Moore
- Armageddon or Calvary: The Conscientious Objectors of New Zealand and “The Process of Their Conversion” by Henry Edmund Holland
- The Silent Division: New Zealanders at the Front, 1914-1919 by Second Lieutenant Ormond Edward Burton
- Historic Trentham, 1914-1917: The Story of a New Zealand Military Training Camp, and Some Account of the Daily Round of the Troops within Its Bounds by Will Lawson
- Gallipoli Diary by Major Edward Percy Cox